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Sentient spider.

The DFour Power Meter Spider is for cyclists already equipped with a Quarq Elsa RS eight-bolt power meter who are interested in the improved functionality of Quarq's latest, DZERO technology. This smart spider lets you keep the components from Quarq (spindle and crank arms) and Shimano (chainrings) that you're currently using, letting you upgrade to more precise power data without forcing you to toss perfectly a perfectly good crank chassis.

If you've got the Prime crank and want to up your training/competitive game, then the upgrade makes obvious sense. If you're already rocking a previous generation of Quarq's 8-bolt powermeter spider, then the reasons are, admittedly, less compelling, and are defined by the internal changes Quarq made to the meter. Of these, the most important is to the heart of the meter itself: the strain gauges and measurement circuitry.

The new design requires less correction in order to maintain accuracy in drastic temperature changes. Fewer corrections mean the DZero also better rations battery life than Quarq's previous power meter models, though when the battery does go out, you can still change it without tools or having to ship the whole thing to the manufacturer. It still incorporates five strain gauges strategically placed throughout the spider, and it's also still got the same claimed accuracy of +/- 1.5%, so its numbers are 0.5% more accurate than most meters.

DZero's accuracy is further boosted by the return of Quarq's 10k dynamic temperature compensation technology, which alleviates the need for constant, mid-race zeroings in variable conditions. Even if it's just coasting for a few seconds or toggling through your head unit to the proper option, it can still be the difference between winning and losing. It's also obnoxious as hell. The DZero is equipped with an auto-adjust schedule based on a constellation of around 10,000 data points that chart how the unit responds to temperatures ranging from zero to 130 degrees Fahrenheit. This lets the power meter figure out the atmospheric details for you with minimal drift, so you can focus on turning the crank, not babysitting it.

Power Balance and Omnical are two additional returning features that record total output and output for either leg individually (Power Balance) and let you swap rings without recalibrating or negatively impacting accuracy (Omnical). As with previous Quarq models, the Dzero communicates to your head unit via ANT+ wireless, but Quarq also adds Bluetooth to this generation. Up till now, we've always tempered the obligatory head unit-compatibility statement by writing that your current computer is likely already compatible with the power meter; now, we can just state outright that it is compatible.

We recognize that there is value in cycling components that can stand up to the elements we often encounter throughout the course of a year of training, but Quarq demonstrates its penchant for being overly thorough by ensuring that the unit's internals can handle comically extreme conditions. The system is waterproof for 30 minutes while submerged under one meter of water, a feature that will come in handy on days you take your bike on the swim leg, too.

As the above implies, the DZero is effectively a catch-all for almost every bit of tech Quarq has thrown at the power meter problem over the past decade. This includes the AxCad accelerometer, which provides cadence information without the need of an additional sensor or magnet. The DZero is also compatible with various training software such as Training Peaks WKO+, Training Peaks, Golden Cheetah, and Strava. Unlike previous Quarq power meters, the DZero's Bluetooth compatibility lets it sync with the Qalvin BLE app to easily tune, tweak, and set zero offsets. That alone might be reason enough to upgrade.

If you're a returning Quarq-ateer, the key to upgrading is ensuring compatibility. To ensure you get the correct upgrade model, you can locate your current model on the chart included below; however, with Shimano-style Quarq models, this process is much easier than with SRAM-style models. Just answer these two questions: Do you have an Elsa RS (released August, 2014)? Are your chainrings Dura-Ace 9000, Ultegra 6800, or 105 5800? If you answered Yes and Yes, then this is the model for you.

Answer Kendrick's Question

This spider requires an Elsa RS crankset, as indicated in the last paragraph of the item description. On your 6800 crank, the spider and drive-side crank arm are one piece, preventing compatibility with the item on this page.

If you want a Quarq power meter that works with your 6800 chainrings, see item QRQ0016 if you have a threaded bottom bracket shell or QRQ0017 if you've got a press fit shell. Feel free to email me at zbonte@backcountry.com if you have any other compatibility questions.